I agree with the others--what a wonderful gift you are giving for your daughters, and how nice was it for the adoptive parents to let you choose their names! From what I've heard, that's not at all very common. And you have wonderful taste in names! I like Julia, Lila, Iris, Leonie, Elisa, and Tess(a). I prefer just Tess to Tessa, but Tessa is lovely, too. I think Julia and Lila, Julia and Iris, Leonie and Tessa, and Julia and Elisa would make lovely pairings. I think Julia and Lila are my favorites, though. Good luck!

Congratulations, and how brave of you to make this difficult choice! I'm sure your little girls will be well-loved and cherished by their new parents.

As Cecelia and Theodora are long and classic, I'd stay in a similar style for the first names, with shorter names, no more than two syllables. I also wouldn't have them end in -a, just so you don't end up with an overly melodic combination.